LEXINGTON, Ky. — With the cool wet spring we have experienced, many producers may be in a hurry to get their vegetable crops off to a quick start. But this may favor losses to root and stem maggots (Figure 1). While early planting may lead to early harvest and high prices in the marketplace, planting into cool or cold soils can result in extended time needed for germination and/or slow seedling growth. Either of these extends the time seeds or small seedlings are vulnerable to attack by root and stem maggots.
Soils have been so wet that it has prevented many fields from being prepared for planting. Some producers may try to work the soil quickly and plant. However, freshly turned over cover crops and winter annual weeds can be attractive for egg laying by root and stem maggot adult flies. For this reason it is good to let the turned cover crops and weeds breakdown for 2 or more weeks before planting or transplanting.
There are several maggot species in Kentucky that attack many different types of vegetables, but seedcorn maggot is probably the most common. Signs of root and stem maggot problems include skips in the row between seedlings and seedlings emerging that are yellowed and spindly. Examining the damaged seeds in skips may reveal hollowed-out seed coats. Seeds planted early are at greater risk when the weather is cool for long periods of time and conditions contribute to delayed, slow germination and seedling establishment.
Reducing Injury from Root and Stem Maggots
Shallow planting in well-prepared seedbeds, and planting sufficiently late for quick germination can help reduce injury. Where possible, heavy cover crops should be turned well in advance of planting to render the field less attractive to egg laying by seedcorn maggot flies in spring. Black plastic raised beds will help to warm the soil and favor rapid seedling establishment. Depending on the crop, insecticide treatments at planting, in transplant water, or as seed treatments may be available to control these insects.
— Ric Bessin, University of Kentucky Extension Entomologist
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